With the popularization of flat panel displays, especially, the liquid crystal panels almost replace the traditional CRT displays by virtue of their characteristics of light weight and compact structure, and also spawn a lot of new use needs and applications. In order to meet different individual needs, the display height, tilt, rotation, etc. need to be adjusted, but the supporting bases provided by display manufacturers have relatively simple functions. Therefore, many professional manufacturers get into this area for intensive research and development. For example, the patent numbered CN201513681U is a typical case. The patent relates to a support assembly structure for LCD display, comprising a bottom support base, a support rod movably connected to the bottom support base, and a beam flexibly connected with the support rod. The front end of the beam is secured with the support surface by means of a linking structure, wherein the linking structure comprises an L-shaped piece, an adjusting screw, a fixing screw and a pressing piece. The support rod is a pneumatic rod with two ends having end shafts. The two shafts are reversely set and the support base is composed of the base and a straight rod connected to the base. The top of the straight rod is provided with a shaft sleeve, and one end shaft of the support rod is inserted in the shaft sleeve; the two ends of the beam are provided with two shaft sleeves and the other end shaft of the support rod is inserted in one shaft sleeve of the beam; the shaft sleeve is connected by means of a linking piece with two supports and can securely fix the LCD display on various desktops or walls through different assembly forms and multi-angle adjustments. The design of the pneumatic rod is not reasonable and shows a weak support. Therefore, the application focuses on the design of a lockable pneumatic rod to lock the angles of the parallel four-link cantilever.